For over 15 years, police have been searching for Madeleine McCann.
Just three years old at the time, Maddie disappeared from her parent's apartment in Praia da Luz, Portugal, on 3 May, 2007.
Parents Kate and Gerry had been enjoying a meal with some friends at a tapas restaurant in their apartment complex that night, and when Kate returned to the apartment to check in on their children, she found that her eldest daughter had gone.
But with no sign of an intruder, police have struggled ever since, despite a number of leads and alleged sightings, to track her down.
Mark Williams-Thomas is an investigative journalist who helped uncover Jimmy Savile's horrific crimes.
Speaking to LADbible for the Extraordinary Lives podcast, he said he pored over the evidence and concluded that Maddie will probably never be found.
The 52-year-old said the most likely scenario is that Maddie woke up in the middle of the night, wondering where her parents were, and went out to look for them.
Williams-Thomas said: "My conclusion is that on that night of Madeleine's disappearance, she woke up, looking for mum and dad, and she'd been told the following morning that if she were to wake up, the parents were only in the tapas bar, which was just across the courtyard.
"What we do know is that her brother and sister had woken up on the previous nights a number of times, and I suspect as a result of that, Madeleine thought, well, where is mum and dad, as they'd been out on those previous nights as well."
He went on: "So I believe she woke up, she left the apartment, we know the apartment was insecure, the back patio door was open to allow some flow of air, it was very hot.
"And so I believe she got up and went wandering looking for her parents."
Watch the full interview here:
In order to get to the tapas bar, though, he said Maddie would have had to go out to a main road, before re-entering the complex towards the courtyard.
However, citing a couple of high profile cases - Genette Tate, who vanished in 1978, and Sarah Payne, who was murdered in 2000 - Williams-Thomas said he believes Maddie was snatched and killed within a matter of hours.
He told us: "Evidence tells us, through the FBI child abduction manual, which is very detailed and very good, because they've got 10 times the child abductions/stranger-child abductions as we've had in the UK, that she would have been dead within 72 hours."
And when asked whether he thought we will ever find out what happened to her once and for all, Williams-Thomas said he believed it was unlikely.
"Sadly, I think it's probably unlikely," he said. "But I always use the caveat that we have to remain positive that one day we will."
You can listen to more of the Extraordinary Lives series here.
Featured Image Credit: James Boardman Archive/Alamy